Abstract : A convergent gun microwave phototube was designed and partially developed. A design solving the problem to preserve the signal on the electron beam between cathode and helix was made, and depends on a laminar convergent flow achieved by using a convergent magnetic field, and electrostatic fields which accelerate electrons along magnetic field lines. That there is negligible conversion of density modulation to velocity modulation of the beam in the gun region by utilizing general principles taken from the theory of low-noise electron guns. Convergent gun phototubes will be superior to linear gun phototubes when a large cathode is needed to provide greater light collection area, such as when an incoherent light source is used, and when a large angular aperture is needed to receive the signal from a coherent light source. Techniques for fabricating phototubes with semitransparent photocathodes have been developed, especially a method for transferring a finished cathode from its forming vessel to the tube. Shot noise output measurements, agreeing with calculated values, have been made on a completed tube. (Author)